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hydraulics / closed conduits

Darcy-Weisbach pipe head loss calculator.

Estimate full-pipe friction and minor head loss from diameter, pipe length, discharge, a supplied Darcy friction factor, and local-loss coefficient.

read the result

Separate distributed and local losses.

Darcy-Weisbach friction loss represents resistance along the pipe wall. Bends, valves, entries, exits, tees, and other fittings are represented here by the supplied sum of local-loss coefficients.

Governing equations

For full circular flow, V = Q/A and A = πD2/4. The friction head is hf = f(L/D)V2/(2g), and the local head is hm = ΣK V2/(2g). The displayed pressure equivalent is Δp = ρg(hf + hm).

Keep the system boundary visible.

  • Static elevation, pump efficiency, pump curves, pressure requirements, and transient effects are not included.
  • Use a friction factor appropriate to the fluid, Reynolds number, roughness, and flow regime; do not copy a value between materially different cases.
  • Entrance, exit, fitting, valve, and equipment losses are only as complete as the supplied ΣK basis.